Program Announcement (PA-02-165) concerning "Race/Ethnic Disparities in the Incidence of Diabetes Complications" invited research on "both biologic and non-biologic factors" and suggested that differences by race/ethnicity and socioeconomic status may be partly due to provider behavior and health care system influences. This theoretically based research builds on the experience and success of earlier studies and investigates the contribution of provider behavior and features of the health care system (both potentially modifiable) to observed disparities in the clinical management of type 2 diabetes mellitus. Novel use of an experimental (factorial) design yields unconfounded estimates of different types of patient, provider and health system contributions to recognized disparities. The project has four aims: 1) to estimate the influence of patient attributes (race/ethnicity, gender, age and SES) on clinical decision making (CDM) for two commonly presented clinical situations (undiagnosed symptoms and signs of diabetes and already diagnosed diabetes with complications); 2) to estimate the influence of physician characteristics (age/clinical experience and gender) on CDM for the presenting cases; 3) to measure the influence of features of the health care system on CDM - both within the US (practice setting, ownership and financial arrangement) and between different systems (requiring the inclusion of other systems for purposes of comparison); 4) to understand the underlying cognitive reasons for the differences in CDM that are observed. This research moves the focus of health disparities research from the behavior, biophysiology and genetic background of individuals (patients) to aspects of provider decision-making and health system influences. Profound policy implications follow from the suggestion that the elimination of health disparities should be sought as much through changes in provider behavior and the system, as through the biophysiology and health care behaviors of those at risk to diabetes and its complications.